Security firm Sophos has taken its partner portal offline and will reset every user's password after it found signs of a potential security breach on the server hosting it.

"Two unauthorized programs were found on the server, and our preliminary investigations indicate that these were designed to allow unauthorized remote access to information," Sophos said in a security alert posted on its website.

The company's staff found the unauthorized applications during a routine security check on April 3, and the potentially compromised server was immediately taken offline for further investigation, the company said.

Sophos could not establish if the data stored in the website's database, which includes partners' names and business addresses, email addresses, contact details, and hashed passwords, had been stolen. However, it decided to proceed under the assumption that it had.

The website will be restored after the security audit is completed and the problem is remediated. However, all user passwords will be forcibly reset as an additional precaution.

The company advised its partners to also change their passwords on other websites where they might have used them, and to be on alert for potential phishing emails that claim to originate from Sophos.

It's relatively common for attackers responsible for breaches that result in stolen email addresses to exploit the known business relationship between the affected users and the victim organization through phishing, in an attempt to extract more information.

In situations where the affected organizations are security firms like Sophos, such phishing attacks can have a high rate of success, because of the inherent trust that exists between users and their security vendors.

"We realize that the site's downtime and the forced password resets may be an overreaction and are sorry for the disruption this will cause, but we would rather cause some inconvenience at this stage than delay as we wait for further information," the company said.

Only the older partner portal, located at https://gpp.partners.sophos.com, has been affected by this security incident, Sophos said. Partners that have already moved to its new Salesforce.com-based portal don't have to worry about the password resets or downtime.